Nuclear magnetic resonance (NMR) is a well-known and widely used technique for obtaining detailed structural information about materials. The usual technique consists of placing a sample of the material to be analyzed in a radio frequency resonator that is located in an intense, uniform static magnetic field; often that of a superconducting solenoid. A radio frequency (rf) pulse is applied to the resonator to induce precessing transverse magnetization in an ensemble of nuclear spins. The signal then induced in the resonator by the precessing transverse magnetization in an ensemble of nuclear spins following the application of the rf pulse permits a detailed structural analysis of the sample material.
This invention pertains to improving the sensitivity of nuclear magnetic resonance measurements by means of a novel, highly sensitive capacitively shortened coaxial resonator. Heretofore, capacitively shortened coaxial resonators have been described in the articles appearing in the Journal of Scientific Instruments (Journal of Physics) Series 2, Volume 2, 1036 (1969) and the Review of Scientific Instruments, Volume 42, No. 4 (April, 1971). Also, attempts have been made to use such resonators as NMR cavities, but, in general, little attention has been paid to them.
The invention of this application provides increased sensitivity by (1) improving the quality (Q) of the resonator, (2) improving the radio frequency filling factor of the resonator, and (3) reducing the external noise contributions that result from acoustic ringing and poor shielding in conventional resonators. Single, double, triple and quadruple tuning of the resonator is also provided.